The invention disclosed herein relates generally to performing storage operations on electronic data in a computer network. More particularly, the present invention relates to systems and methods for conserving removable media usage in a storage network.
Current storage management systems perform many different types of storage operations including backup operations, restore operations, and archive operations. For example, during a backup operation, data stored on a client computer or other system is communicated via a network or other communication means to a storage device such as a tape drive, optical library, Redundant Arrays of Inexpensive Disks (RAID), CD-ROM jukebox, or other device. Clients are backed up periodically, and a number of different systems and methods exist for backing up client data.
For example, rather than backup all of the data on a client every time a backup is performed (also known as a full backup), incremental backups are sometimes performed copying only those blocks of data on the client which have changed since a prior backup. Thus, a system might initially make a full backup of a client and then only make incremental backups for a given period until the next full backup is scheduled.
One advantage of incremental backups is reduced storage media usage. For example, if a full backup utilizes one entire tape, then performing a daily full backup will consume approximately 30 tapes in a month. If a daily incremental backup only consumes ⅙ of a tape, however, and full backups are only performed once per week between incremental backups, then only about 8 tapes would be required—a savings of 22 tapes. Thus, incremental backups are a widely used form of backing up client data in current storage management systems.
Once the data has been backed up, however, even with incremental backups, it is not generally retained indefinitely since this would, among other things, use an extremely high number of tapes or other storage media over time. Instead, aging rules are often applied and backed up data is frequently deleted or moved to other media after a specified period of time. For example, data might be backed up daily for a month, then only monthly copies kept for a year, and then only yearly copies kept for 7 years until the data is eventually deleted.
When data is aged, the backed up data is often copied from one set of storage media to another set of media using a variety of techniques. The original tapes which stored the original backed up data (the primary copy) may then be returned to a “scratch pool” of available media for reuse. For example, one common technique used to copy backup data and other data is to perform an auxiliary copy. An auxiliary copy generally copies data from one set of media, such as a tape set storing full and incremental backups for given time period, to another set of media generally using a network pathway, such as a storage area network or other network, dedicated to performing storage operations. The tape set or other media which stored the original incremental backups (or possibly all data copied by the auxiliary copy) is then returned to the scratch pool for reuse.
One drawback with aging and copying backup copies of data is that the additional copies require additional sets of media. Thus, for example, three additional tapes are required to perform an auxiliary copy of a backup copy containing a full backup on one tape and incremental backups on two additional tapes—the three original tapes are copied to three additional tapes. One possible solution is to perform a selective auxiliary copy which copies only the full backup, but even this method requires at least one tape in addition to the tapes used for storage of data on the primary backup copy.
There is thus a need for systems and methods which reduce removable media usage during aging operations and other operations in storage management systems.